1. Field of the Invention
The present invention relates to a nozzle for a fire hose.
2. Description of the Related Art
Conventionally, a fire hose nozzle connected to the tip end portion of a fire hose is provided with a mechanism for varying the pattern in which water is discharged in a plurality of ways. For example, in a fire hose nozzle described in Japanese Unexamined Patent Application Publication H9-285561, a first cylinder is joined screwably by a screw to the outer periphery of the tip end of a fixed nozzle main body which is connected to the tip end portion of a fire hose, and a second cylinder is joined screwably by a screw to the outer periphery of the first cylinder. By rotating the first cylinder such that the first cylinder moves forward or backward along the fixed nozzle main body, the surface area of an inlet to a flow path on the inside of the first cylinder varies, thus varying the flow rate of a rectilinear rod-form water jet that is discharged forward from the inner flow path. By rotating the second cylinder such that the second cylinder moves forward or backward along the first cylinder, the area and form of an outlet from an annular flow path between the first cylinder and second cylinder varies, and thus the form (tubular form and radial form) and flow rate of an atomized water spray that is discharged from the annular flow path is controlled. Hence a selection may be made among a plurality of discharge patterns, consisting of a rod-form discharge pattern in which water is discharged as a linear rod-form water jet, a spray-form discharge pattern in which an atomized water spray is discharged in a tubular or radial form, and a combination discharge pattern combining the rod-form water jet and the atomized water spray.
However, in this conventional fire hose nozzle, when the discharge pattern is varied at a fixed water pressure, the surface area of one or both of the inner flow path inlet and the annular flow path outlet varies, causing the flow resistance to vary, and hence the total water discharge amount (total flow) from the nozzle fluctuates. This causes a problem in that the load acting on a discharge pump fluctuates when the discharge pattern is varied using the fire hose nozzle. The load acting on the firefighter also fluctuates when the discharge pattern is varied using the fire hose nozzle.
Further, in this conventional fire hose nozzle, the first cylinder must be rotated to control the rod-form water jet, and the second cylinder must be rotated to control the atomized water spray. Hence, to choose from among the plurality of discharge patterns described above, the firefighter must operate the two cylinders manually. A simpler method of varying the discharge pattern in a shorter time period is therefore desirable.
Furthermore, in the combination discharge pattern combining the rod-form water jet and the atomized water spray, the atomized water spray that is discharged radially functions to lower the temperature of the flames that are directly in front of the firefighter and block off the smoke, and is therefore used by the firefighter as a self-protection water screen. It is desirable to be able to control the protection capability of this self-protection water spray (for example, the thickness or flow rate of the water screen) according to the situation at the scene of the fire. In the conventional fire hose nozzle described above, however, when the water discharge amount of the atomized water spray is altered, the form of the spray also changes, and hence it is difficult to control the protection capability of the water spray while maintaining the self-protection radial form thereof.